1. Field of the Invention
The present invention relates to a rectifier device for an alternator mounted on an automotive vehicle.
2. Description of Related Art
An alternating current generator, referred to as an alternator, is mounted on an automotive vehicle for charging an on-board battery and for supplying electric power to various devices mounted on the automotive vehicle. Since a large amount of current flows through rectifier elements mounted on the alternator, the rectifier elements are mounted on a heat-radiating plate. An example of such a rectifier device is disclosed in JP-B2-3771637. The rectifier element is composed of a disc portion, a semiconductor element mounted on the disc portion and a lead wire connected to the rectifier element. The rectifier element is connected to the disc portion with solder and sealed with silicone rubber or resin. The rectifier element is mounted on the heat-radiating plate by inserting an outer peripheral portion of the rectifier element having a knurl portion.
In a conventional structure of the rectifier device, the rectifier element is forcibly inserted into a mounting hole of the heat-radiating plate. Since the mounting hole formed in the heat-radiating plate has a diameter that is uniform throughout a thickness of the heat-radiating plate, a local stress is imposed on certain portions of the semiconductor element during a course of forcible insertion of the rectifier element into the heat-radiating plate. This may result in causing damages in the semiconductor element.